Phase control in high frequency coupled circuits



P 2- E. SCHUFZE-HERRINGEN ETYAL 7 2,297,255

PHASE CONTROL IN HIGH FREQUENCY COUPLED CIRCUITS Filed July 22, 1939 2Sheets-Sheet l 'FKITZ Guzzm'ann by W I Affornqg Sept. 29, 1942.2,297,255

PHASE comm IN HIGH FREQUENCY COUPLED CIRCUITS E. -SCHULZE"HERRINGEN ETAL Filed July 22,1959 2 Sheets-Sheet 2 //7 untars: ErichShu/ze-Herringen Fritz Gufzmarm A for/veg example of the invention.

Patented Sept. 29, 1942 PATENT OFFICE PHASE CONTROL IN HIGH FREQUENCYCOUPLED CIRCUITS Application July 22, 1939, Serial No. 285,846 InGermany July 26, 1938 Claims.

It is in many cases necessary in high frequency transmission toaccurately stabilize the phase relation of coupled oscillatory circuits.Up to the present time only approximate methods have been used, such as,for instance, by the matching of two adjacent circuits to obtain amaximum current ratio or by other similar means.

Such operations, when applied to more than two circuits, entail stillfurther complications and expenditure of time in order to obtainaccurate adjustment.

The present invention discloses a means of effecting fast and accuratephase control under load, in which the correct setting is obtaineddirectly through the measurement of the phase angles of the currentsflowing in the coupled cir cuits. The proposed method has no effect uponthe correct adjustment of a preceding circuit.

Now, correct phase adjustment is attained when the currents of twoadjacent circuits, are in quadrature. The actual measurement of thesephase conditions may be accomplished by the use of a bridge and ameasuring instrument. This bridge determines the condition of phasequadrature on a zero-reading instrument. The invention is illustratedbelow in Figs. 1-4 showing some typical applications with reference tocircuit diagrams.

Fig. 1 shows the device in its simplest application, in which only twomutually coupled circuits are to be regulated. In the illustratedarrangement a transmitting tube I works into an impedance R through twocoupled circuits KI and K2. The phase adjustment of the circuit K2 isaccomplished, for example, by means of the variable inductance 2. Thephase bridge P is used to control this adjustment and constitutes anThis phase bridge consists of the rectifiers 3 and 4, the impedances 5and S, th zero-reading instrument I and its internal series impedance B,the coupling coils 9 and 10 with their shunt lmpedances ll, l2, and 83.The coupling coils 9 and H! are arranged, for example, as currentconverters; coupling coil 9 is coupled to the circuit K2, and coil ID tothe circuit Ki. The meter 1 of the phase bridge registers zero when thevoltage across the impedances H andv i2 has a phase difference of 90degrees with respect to the voltage drop appearing across the impedancel3.

circuit conditions the circuit K2 is phase-controlled by adjustment ofthe variable inductance 2 by'means of the phase bridge P and the zeroreading meter 7 while the circuit KI' is adjusted for minimum platecurrent under the control o Depending upon the variable inductance H, asindicated from the reading of the plate-ammeter J. The alteration of theconditions in'circuit Kl by the variable inductance M will not all'ectthe reading of meter 1 of the phase bridge P, because the.

phase indication of the zero reading meter 'is independent of theamplitude of current changes in the phase bridge.

The invention is not confined to the illustrated application of Fig. 1,which only involves the phase adjustment of two coupled circuits, but islikewise applicable to a larger number of coupled circuits. Under suchconditions a phase bridge of the aforementioned nature, as illustratedin Fig. 1,- can be connected to each two adjacent coupled circuits. 'Atypical illustration of this arrangement is shown in Fig. 2, in whichfour cou pled circuits Kl, K2, K3, and K4 are shown as well as thecorresponding phase bridges Pl, P2, P3. The phase adjustments are begunwith the last circuit K4 with the help of the phase bridge P3. Then K3is controlled with P2, K2 with Pl,

and finally K|,- is adjusted to the plate current minimum, which isnoted on the ammeter J.

A further application, which is illustrated in Fig. 3, shows the case ofan antenna coupling matched to a cable. In Fig. 3, AK is an antennacircuit and K a cable circuit. The phase ad-- justment of the antennacircuit AK with respect to the cable termination is made by using thephase bridge P2 and the phase adjustment of the cable circuit with itstermination by use of the phase bridge PI.

The phase bridge PI is coupled to circuit K by the coil S2 as alreadydescribed. The other branch of the phase bridge is coupled across thecondenser C3 inductance L and impedance RI, Cable voltage appearsvacross the condenser C3 according to circuit conditions, and is in phasewith the current in the coil S2. Accordingly, since the phase bridgeindicates voltages in quadrature by a zero reading, for such a readingthe voltage across the impedance RI must be in quadrature with thecablepotential.

l Furthermore, it is important faster as the cable termination isconcerned to couple the proper impedance to the cable, so that thecoupled te mination impedance will match the characte.'

istic impedance of the cable '(for, example 66 ohms) If the circuit KKand the phase bridge Pl are in proper phase adjustment, the cable loadappears as a pure resistance and the indh cation of the crossed-coilmeter measuring fizztrument shows only a pure effective resistance.

It a pure inductance or other form of irnp eda'nce be used as a couplingbetween the cable and antenna circuits, so that neither the circuit AKnor the circuit K is brought out of adjustment, the terminal impedancecan through the adjustment of this coupling be brought to a zero ,valueby making a simple impedance reading on the meter Q. The matchingadjustment of the antenna circuit to the cable can thus be accomplishedsimply and quickly by three manual operations, each for a separatecomponent.

The. measurement of the cable terminal impedance has previously beenaccomplished by the separate use of a voltmeter and an ammeter. To makepossible a simultaneous reading of the impedances and to avoid a doublereading, it is proposed, that the impedance measurement be made with thehelp of a crossed-coil instrument. Th s instrument is designated in Fig.3 by the letter Q. It is well known that a, crossed-coil meter indicatesa current ratio. In th arrangement of Figure 3 one coil circuit of thecrossedco-il meter carries the cable current through a rectifier GI anda coupling coil SI, and the other coil circuit carries a currentproportional to cable voltage as delivered to the rectifier G2, thevoltage across which is determined by the potentiometer Cl, C2 and whichvoltage is proportional to cable potential. The crossed-coil meter will,because it measures the voltage to current ratio, indicate ohms, e. g.according to the use of a 60-ohm cable a variation from about 30 to 90ohms may be noted, The phase adjustment of the antenna unit, withrespect to the coupling circuit, as it is shown in Fig. 3, isaccomplished by the following means:

'The antenna circuit is adjusted in phase by the zero method variableinductance V2 and the phase bridge P2. Then the cable circuit K isphase-adjusted by the zero method with the variable inductance VI andthe. phase bridge PI. The correct impedance for terminating the cableiscoupled into the circuit through the variable coupling KV with thehelp of the crossed-coil meter Q, that is, the variable coupling KV isregulated to 60 ohms to terminate a 60-ohm cable.

The phase bridge may also be used automatically to adjust one or morecircuits to correct phase relation. To illustrate, when a misadjustmentoccurs in the phase bridge as indicated by negative or positivedirection of current, this current can be used to control respectively arelay and a motor, which motor is in motion as long as thephase-adjusting operation is be made, that is, until the currents in thephase bridge are balanced to a meter reading of zero, whereupon themotor is automatically disconnected by the relay. In the phaseadjustment of more than two circuits the corrections can beaccomplished, for example, as shown in Fig. 2: First,

the variable inductance V4 is used to adjust circuit K4 through the helpof phase bridge P3. Then, after the setting of this circuit, thecirc'uit K3 is automatically brought into operation through theoperation of a relay, which also releases the phase bridge P2 fromoperation. In a similar manner circuit K3- is adjusted by the inductanceV2. and subsequently the circuit K2,

may be automatically set by the phase bridge PI and then released by arelay. After the adtion provision is made in a similar way for the phasecontrol of a plate oscillatory circuit. Since plate oscillatory circuitsoperate with small reactive loads, e. g. loads with real to imaginarypower ratios of 4:1, the phase adjustment of 180 degrees between thealternating-current plate voltage and the alternating-current controlgrid voltage is distorted and direct phase opposition no longer exists.This condition is, however, necessary for good operating efliciency ofthe transmitter, since the efliciency is 1 7'H-cos Consequently, whenboth circuits are in phase the value of cos is unity, from which itfollows that efficiency is then at a maximum. The invention furthershows a method for reducing the phase relation of 180 degrees betweengrid and plate potentials to 90 degrees so that then with the help ofthe above-mentioned phase bridge P this voltage measurement can be made.

An example illustrating a phase adjustment of 180 degrees is shown inFig. 4, in which RI and R2 are the tubes of a push-pull stage. CI and C4are tank circuit condensers, C5 and C6 plate blocking condensers, and LIthe coil of the oscillatory circuit. The secondary circuit of thetransformer K is loaded by the impedance Ra.

The push-pull part of the phase bridge P is connected across thecondensers C3 and C4 of the plate circuit, and the rectifier part acrossthe impedance Rb. The potential drop across the impedance Rb difiers inphase from the alternating-current control voltage by 90 degrees, andthe resistance Rb is small in comparison with the reactance o!the'condenser C1. If the potential drop across the resistance Rb is in Iquadrature with the voltage appearing across the reactances C3 and C4,then the meter 1 of the phase bridge P registers zero. Therefore, onlywhen the voltage drop across the resistor Rb is 90 degrees out of phasewith the grid potential of the tube RI, as shown by the zero-reading onthe meter I, can a phase difference of 180 degrees exist between thealternating-current voltages of grid and plate of the tube RI.

Excitation of the phase bridge P may further be brought about by using acurrent converter. In this application the currents in the capacitatlveand inductive branches of the receiving circuit are respectively inquadrature with the alternating-current plate voltage, and consequently,in a case of an additional phase difference between the grid or platepotentials respectively, it

is not necessary to operate the phase bridge. The phase adjustment of aplate oscillatory circuit by the use of the phase bridge P likewiserelies upon the automatic adjustment of the plate oscillatory circuit.

What is claimed is:

1. In a high frequency system, a push-pull circuit, comprising two tubeseach having at least a cathode, a grid and a plate, a grid circuitformed between the said grids and the said cathodes, a. plate-circuitconnected across the said plates and the said cathodes, aphase-comparing circuit consisting of a differential bridge circuitcomprising a pair of unilateral conducting devices. and means adapted toimpress voltages from the said grid circuit and the said plate circultupon the said difierential bridge circuit in parallel and push-pullrelation respectively for determining the phase relation therebetween.

2. In a high frequency system, a pair of oscillatory circuits coupledwith one another, a differential bridge circuit comprising a pair ofunllateral conducting devices and a measuring instrument connectedthereto, means for applying alternating voltages derived from one ofsaid oscillatory circuits to said unilateral conducting devices inpush-pull relation, means for applying alternating voltages derived'frorn the other of said oscillatory circuits to said unilateralconducting devices in parallel relation, and tuning means associatedwith at least one of said oscillatory circuits for adjusting the phaseangle of the currents in said oscillatory circuits inorder to obtain apredetermined reading upon said measuring instrument.

3. In a high frequency system, a pair of oscillatory circuits coupledwith one another, a differential bridge circuit comprising a pair ofunilateral conducting devices and a zero-reading measuring instrumentconnected thereto, means for applying alternating voltages derived fromone of said oscillatory circuits to said unilateral conducting devicesin push-pullrelation, means for applying alternating voltages derivedfrom the other of said oscillatory circuits to said uniover a deviceadapted to impose a phase shift of 90 degrees upon the alternatingvoltages applied to said bridge circuit.

5. A high frequency system according to claim 1 wherein said gridcircuit is associated with said difierential bridge circuit over adevice adapted to impose a phaseshift of 90 degrees upon the alter'nating voltages applied in parallel relation to said 20 bridge circuit.

ERICH SCHULZE-HERRINGYEN. FRITZ devices in parallel relation}

